Some of the disclosed embodiments relate to a hybrid vehicle or an electric vehicle, and in particular to a power source device for a vehicle provided with a high-voltage battery that supplies power to a driving motor.
Related art hybrid vehicles or electric vehicles are provided with a driving motor, and a high-voltage battery that supplies power to the driving motor. A relay contact is arranged for wiring the driving motor and the high-voltage battery. According to operations that begin and end driving, the relay contact is turned on and off.
FIG. 1 is a block diagram showing a structure of significant or main parts of a related art power source device for a vehicle used for a hybrid vehicle or an electric vehicle. Such a related art power source device for a vehicle includes: (i) a driving motor 1a, (ii) a high-voltage load 1 that is a circuit attached to the driving motor 1a, (iii) a high-voltage battery 2 that supplies power to the high-voltage load 1, and (iv) a relay contact 3 that is arranged on a path by which the high-voltage battery 2 supplies power to the high-voltage load 1, and which opens and closes the path. The high-voltage load 1 is supplied power from the high-voltage battery 2 via the relay contact 3. Furthermore, in the case of a hybrid vehicle, the high-voltage load 1 having the driving motor 1a also functions as a generator that works together with an engine (not shown).
A relay controller 40 within a high-voltage power source controller 4 controls on and off operations of the relay contact 3. The relay controller 40 is provided with control signals corresponding to operations of a power switch (not shown) that begins and ends driving, and the relay contact 3 is turned on and off. Based upon the operation that begins the driving, the relay controller 40 receives a control signal that requests that the relay contact 3 be turned on. When the relay contact 3 is turned on, the relay controller 40 supplies excitation power to a relay coil (not shown) arranged in the vicinity of the relay contact 3.
The high-voltage power source controller 4 has a power source circuit 41 that supplies power to the relay controller 40, and the power source circuit 41 is supplied with power from a low-voltage auxiliary device battery 6, which is described below. If the relay controller 40 receives, by the operation that ends the driving, a control signal that requests that the relay contact 3 be turned off, the relay controller 40 stops feeding power to the relay coil and turns the relay contact 3 off. The high-voltage battery 2 stops supplying power to the high-voltage load 1.
A related art power source device for a vehicle also includes: (i) a low-voltage load group 5 that is an on-board auxiliary device group, and (ii) a low-voltage auxiliary device battery 6 that supplies power to the low-voltage load group 5. A step-down circuit 70 within a DCDC converter 7 is connected between: (a) a connecting node of the high-voltage load 1 and the relay contact 3, and (b) a cathode terminal of the low-voltage auxiliary device battery 6. Normally, the step-down circuit 70 steps down an output voltage (absolute value) of the high-voltage battery 2 that has been received through the relay contact 3 at the time of driving and provides it to a low-voltage auxiliary device battery 6 side terminal. The step-down circuit 70 is controlled by a control signal from a controller (not shown). The DCDC converter 7 has a power source circuit 71 that supplies power to the step-down circuit 70, and the power source circuit 71 is supplied power from the low-voltage auxiliary device battery 6.
The power source circuit 41 that supplies power to the relay controller 40 is supplied power from the low-voltage auxiliary device battery 6. If the driving of the vehicle begins, in order to turn on the relay contact 3, the relay controller 40 supplies excitation power to the relay coil arranged in the vicinity of the relay contact 3. At this point, if the remaining capacity of the low-voltage auxiliary device battery 6 is low, then the power circuit 41 cannot supply power to excite the relay coil.
Japanese Published Patent Application 2007-244034 (JP 034) discloses a power source device for a vehicle that increases a possibility of transferring a vehicle state to a traveling state, even in a state in which an auxiliary device battery (low-voltage auxiliary device battery 6) voltage decreases. In this power source for a vehicle, a system main relay SMRP is arranged in parallel with a system main relay SMRB (relay contact 3). Drive electricity of the system main relay SMRP is smaller than that of the system main relay SMRB. A controller controls opening and closing of the system main relays SMRB and SMRP.
If the auxiliary device battery voltage decreases, the controller closes the system main relay SMRP, the power source voltage of the main battery (high-voltage battery 2) is supplied to a DC/DC converter (step-down circuit 70), and the DC/DC converter steps down the power source voltage and provides it to the controller. By so doing, the controller closes the system main relay SMRB and shifts the vehicle state to a traveling state.